JPH0625892B2 - Fixing device - Google Patents

Description

The present invention relates to a heating device for heat-treating an object to be heated, and more particularly to a fixing device effective for an image forming apparatus.

As shown in FIG. 1, generally in a fixing device,
The surface temperature of the heating roller 1 pressed by the pressure roller 2 and rotatably provided on the fixing side plate 8 by the bearing 7 is brought into contact with, embedded in, or brought close to the surface temperature of the heating roller 1 heated by the heater 5. The temperature is detected by the temperature detecting means (not shown), and the heater 5 is detected by the temperature control circuit which receives the detection signal.
The electric power applied to the roller 1 is controlled so that the surface temperature of the roller 1 is maintained within an allowable range.

However, if the heater 5 is not controlled due to a failure of the temperature control circuit, the heating roller 1 may be heated to an abnormally high temperature, and the roller itself and peripheral members may be burned or even a fire may occur. Therefore, in order to prevent this excessive temperature rise, a temperature fuse 11 is provided close to the heating roller 1, and this temperature fuse 11 is inserted in series in the electric path of the heater 3 via the electrodes 6 and 12, and this temperature fuse is inserted. The heat from the heating roller 1 is melted and blown by 11 to prevent the heating roller from overheating.

However, since the conventional temperature fuse 11 is arranged so as to receive the radiant heat from the heating roller 1, it is easily affected by the air flow around the heating roller 1 and the fuse 11, and the heating roller 1 actually reaches the dangerous temperature. However, there is a possibility that the temperature fuse 11 will not be blown yet, and the amount of radiant heat received will be quite different only because the distance from the heating roller 1 is different. High accuracy is required for the position, otherwise, the temperature fuse 11 frequently melts even though the temperature does not abnormally rise, or does not melt even if the temperature rises abnormally. Furthermore, if only the radiant heat from the heating roller 1 is used, the temperature fuse may be exceeded after the heating roller 1 reaches an abnormal temperature due to the heat capacity of the temperature fuse 11.
There is an inconvenience that it takes a long time until 11 melts, that is, a response time is long, and the temperature of the heating roller 1 is increased during that time. In particular, the heating roller 1 has a small thickness and a small heat capacity. This inconvenience is great in combination with the large capacity heater 5.

Therefore, a fixing device has been proposed in which the temperature fuse 11 is arranged at a position where it receives the radiation from the heater 5, but the influence of the inner surface state of the heating roller 1 and the influence of the copy speed and the like are large, and the fixing device is Compared to the type that operates by receiving radiant heat, the melting characteristics during abnormal conditions are not sufficiently improved, and the temperature fuse 11 melts even if there is no abnormal temperature rise, or the temperature fuse during abnormal conditions becomes longer and is fixed. It also occurs when the device is severely damaged.

If the temperature fuse 11 is provided above the heater 5 and near the opening of the hollow portion of the heating roller 1, the temperature fuse 11 is inevitably exposed to the high temperature atmosphere of the heating roller 1. Therefore, it is unavoidable to use a high melting temperature rating for the temperature fuse 11, and this causes the heat capacity of the fuse to be very large, so the response speed of the melting at the abnormal temperature rise of the heating roller becomes slow. There was a drawback.

The present invention solves the drawbacks due to the above-mentioned problems, omits heat that becomes noise in heat as heat sensitive information, receives accurate heat information, achieves improvement in responsiveness, and stable safety. The purpose is to secure.

The present invention is characterized in that the excessive temperature rise prevention member is arranged below the heat source provided inside the heat fixing roller.

Next, an embodiment of the fixing device according to the present invention will be described with reference to the drawings.

FIG. 2, FIG. 3, and FIG. 4 show an embodiment of a fixing device according to the present invention of a type that utilizes radiant heat from a conventional heater. FIG. 2 is a cross-sectional view of the vicinity of the temperature fuse installation section, where 1 is a heating roller made of aluminum as a heating and fixing roller,
Reference numeral 2 is a pressure roller in which a silicon rubber elastic layer 4 is coated on a core metal 3, and 5 is a heater as a heat source provided inside the fixing roller 1. Electric power is supplied through an electrode 6 to the heating roller 1 Is heated from the inside. The heating roller 1 is rotatably fixed on the fixing side plate 8 by a bearing 7. The pressure roller 2 is also rotatably supported by the bearing 9, and is a pressure plate.
A pressing means (not shown) urges the fixing roller 1 to press the fixing roller 1 by a predetermined pressure, and the heating roller 1 is rotated by the heating roller 1. Reference numeral 11 denotes a temperature fuse as an excessive temperature rise prevention member, which is provided at a position where it can receive radiant heat from the light emitting section 5a of the heater 5 and below the heater 5.

FIG. 3 is a perspective view of a temperature fuse portion of the fixing device according to the present invention, and FIG. 4 is a front view showing the positional relationship between the fixing roller, the temperature fuse, and the lead wire. 3 and 4
In the figure, the temperature fuse 11 is the heater 5 in the heating roller 1.
2 is provided below the position, and as described above with reference to FIG. 2, it is arranged at a position near the hollow outlet of the heating roller 1 capable of receiving the radiant heat from the heater 5.
Lead wires 11a and 11b are provided at both ends of the temperature fuse 11, the lead wire 11a is connected and fixed to an electrode 6 connected to the heater 5, and the lead wire 11b is an electrode connected to an external power source. Connected to 12 is fixed. The lead wires 11a and 11b meander in a S-shape or an inverted S-shape, for example, in order to absorb more heat from the heater 5. The lead wires 11a and 11b are connected to the heater 5
It is located at a position where it is directly exposed to radiant heat from.

Now, considering the case where the heater 5 continues to light due to a failure on the main body side, the lead wires 11a and 11b also receive radiant heat from the heater 5, so the lead wires 11a and 11b themselves become hot, The heat of the fuse 11 is hard to escape, and the temperature fuse 11
The temperature rising speed of the product becomes faster, and the responsiveness of melting is good.

Since the lighting time of the heater 5 is short during the normal operation of the fixing device, the influence of the shape of the lead wires 11a and 11b of the present embodiment on the temperature of the temperature fuse 11 in comparison with the conventional one. Is almost the same as the conventional example.

Further, during continuous sheet feeding, the temperature of the atmosphere inside the heating roller 1 is lower than the temperature of the atmosphere above the heater 5 due to convection and the like. Temperature fuse supplied with heat by a low temperature atmosphere
The temperature of 11 also hardly rises, and the rated temperature for melting the temperature fuse 11 can be lowered. Therefore, the heat capacity of the temperature fuse 11 is smaller than that of the conventional one, so that the response to the heat becomes faster and the fusing time of the temperature fuse 11 at the time of abnormality causing excessive heating of the heating roller 1 by the heater 5 is further increased. It can be shortened.

Although the lead wires 11a and 11b are meandered in the above embodiment, a straight wire may be used as in the conventional case, and the above operation is performed by disposing the temperature fuse 11 at a position below the heater 5. It can be fully achieved.

In addition, the temperature fuse 11 and the lead wires 11a, 11b are painted in black by using a member having good thermal conductivity to improve their heat absorption and further improve the melting response characteristics of the temperature fuse 11. Can be improved.

Further, in the above-described embodiments of the present invention, the heat-sensitive member is focused on for description. However, it has been found that the heating device generally has a large variation in the inner surface of the heating roller during manufacturing, which has some influence on the thermal response.

The following examples can further improve the thermal responsiveness in each of the above examples.

As described above, the temperature fuse 11 (may be a thermistor or the like) and the lead wires 11a and 11b are perpendicular to the moving direction of the heating roller 1 having the heater 5, and the plane S including the heater 5 is included.
(The heater 5 is provided at the center of the roller. In this embodiment, the heater 5 is provided below the half section including the center of the roller) (gravitational direction). More preferably the heat-sensitive member within the semicircle of the roller
It is more suitable for the present invention that the heat-sensitive portion 11 is more preferably provided most of the lead wires 11a and 11b within the semicircle of the roller because the response can be further improved.

By the way, the inner surface of the heating roller 1 has a large variation in manufacturing, and the unevenness (roughness) of the inner surface of the heating roller 1 is large and small. Although there is usually a method of roughening the surface to enhance the heat absorption, there is a large difference in the degree, and the heating roller 1 as an individual product has an extremely large variation range. Therefore, the amount of heat released from the inside of the heating roller may sometimes differ greatly depending on the rollers and the circumferential angle of the rollers.

As described above, the present invention having good responsiveness may be greatly affected by such variations. Therefore, in this embodiment, either the chemical polishing treatment, the alumite treatment, or the chemical polishing treatment and the alumite treatment is adopted as the heating roller inner surface treatment. In terms of the degree, the effects are high in the above-mentioned order, and are also strong against the change with time.

In this way, it is a more preferable embodiment of the present invention to treat the unevenness of the inner surface of the heating roller 1 to reduce the range of the variation and eliminate the variation factor of the responsiveness in manufacturing.

In addition, in the above-mentioned embodiment, the heat fuse having the heat melting property is used, but other than this, the one using the bimetal, the temperature switch using the magnetic material and the like can be used. Further, the material of the heating roller may be stainless steel other than aluminum.

As described in detail above, the present invention improves the thermal response and can detect the roller surface temperature more accurately, and thus has a higher degree of safety.

The heat fixing roller referred to in the present invention includes all rollers having an end opening and those having a nonuniform diameter.

As described above, with a simple configuration in which the position of the excessive temperature rise prevention member is installed below the heat source, the cutoff time of the power supply path to the heat source at the time of abnormality is shortened, and at the same time during normal continuous use. Also, it is possible to provide a highly reliable fixing device in which the excessive temperature rise prevention member does not shut off the power supply path.

Further, according to the present invention, by providing chemical polishing and anodic oxidation (alumite) on the inner surface of the heating roller, it is possible to provide a heating roller having a stable inner surface state and high mass productivity with no change over time and having high temperature distribution. Can be done. The present invention is particularly effective when used in a fixing device having a temperature fuse that utilizes radiation as described in the embodiments, and provides a highly reliable fixing device having a high temperature fuse response. Was completed.

[Brief description of drawings]

FIG. 1 is a perspective partial view of a conventional fixing device, FIG. 2 is a cross-sectional explanatory view of the fixing device according to the present invention, FIG. 3 is a perspective partial view of FIG. 2, and FIG. FIG. 1 ... Heating roller, 2 ... Pressure roller 5 ... Heater, 6 ... Electrode 7 ... Bearing, 8 ... Fixing side plate 9 ... Bearing, 10 ... Pressure plate 11 ... Temperature fuse, 11a, 11b ...... Lead wire 12 …… Electrode

 ─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP-A-59-34574 (JP, A) JP-A-53-26134 (JP, A) JP-A-56-107277 (JP, A) JP-A-56- 107278 (JP, A) JP 59-60457 (JP, A) JP 50-93656 (JP, A) JP 56-137375 (JP, A) JP 54-6560 (JP, A) Actually open 55-42893 (JP, U) Actually open 48-47347 (JP, U) Actually open 56-58664 (JP, U) Actually open 54-42952 (JP, U) Japanese Patent Publication 2-48903 (JP, B2)

Claims (1)

[Claims] 1. A heating and fixing roller having a heat source for emitting a heat ray therein, and an excessive temperature rise preventing member for detecting an excessive temperature rise of the heat fixing roller and shutting off an electric power supply path to the heat source. A fixing device in which the excessive temperature rise prevention member is arranged to directly receive a heat ray from the heat source, wherein the excessive temperature rise prevention member is arranged below the heat source.